Exhaust tube for internal combustion engines



g- 1932 F; T. JRGENS 1,869,749

EXHAUST TUBE FOR INTERNAL COMBUSTION ENGINES Filed Oct. 17. 1929 INVENTOR P1121 2 TIIQE ATTORNEYS Patented Aug. 2, 1932 UNITED STATES PA-TENT OFFICE FINN T. IBGENS, OF MILWAUKEE, WISCONSIN, ASSIGNOB TO OUTBOARD MOTORS B- .POBATION, OF MILWAUKEE, WISCONSIN, A. CORPORATION OF MICHIGAN EXEAUST TUBE FOB INTERNAL COMBUSTION ENGINES Application fled October 17, 1999. Serial No. 400,218.

type.

It is well known that a two-cycle engine, such as that used in outboard motors, exhausts and admits simultaneously, so that there is only avery slight pressure tending to discharge the exhaust. Consequently, if a straight exhaust pipe is used, a very heavy pulsation is set up therein, resulting in back pressure,*particularly if the pipe is restricted. Such pulsation and back pressure cause a w material drop in power.

In outboard motors where the exhaust takes place under water for the purpose of silencing, it is necessary to have an expansion chamber between the head of the engine and the submerged exhaust outlet. The present invention provides an effective expansion chamber in this position.

The principal objects of the invention are to increase the volume of the expansion chamber and to eliminate the pulsations which are set up in a straight exhaust pipe and which have a material effect on the power developed by the engine. This object is attained by tapering the pipe from the inlet end to the outlet end thereof, the inlet end being of larger cross section than in the case-of a straight pipe. It has been found by test that a plpe of this character eliminates the above menume of the exhaust expansion chamber.

The invention is fully disclosed by way of example in the following description and in the accompanying drawing, in which Figure 1 is a vertical elevation of an voutboard motor equipped with the invention and applied to a boat which is shown in section;

Fig. 2 is a front or rear elevation of the exhaust tube;

Fig. 3 is an elevation at right'angles to Figure 2 Fig: 4 is a fragmentary rear elevation of the motor, showing the upper end of the exhaust tube; and

Figs. 5, 6 and 7 are sections on the lines tioned pulsations and also increases the vol- 55, 6--6 and 7-7 respectively of Figure 1.

Reference to these views will now be made by use of like eharacterswhich are employed to designate corresponding parts throughout.

The numeral 1 indicates in general the usual motor structure which has a clamp 3 adapted for attachment to the transom 4 of a boat.

The adjustments of this assembly are con Kent 101131 and therefore need not be described ere.

At the lower end of the motor structure is the usual propeller shaft housing 5 on which is formed an anti-cavitation plate 6, preferably as an integral ovoid cross section.

The rear or trailing end of the plate is formed with a mouth 7 beneath its upper and lower surfaces. The details of this plate are described in the co-pending application of King and Lockwood, Serial No. 290,306, filed July 5 1928 and allowed April 15, 1929.

'1 o-the cylinders of the engine is applied an exhaust manifold 8 which in turn communicates with the exhaust tube now to be described. The tube is of an approximate T- shape in elevation, as shown in Figure 2, and comprises a head 9 which is securedtbetween and in communication with the ends of the exhaust manifold 8.

Due to the necessity of an expansion chamber as already outlined and the compact design of an outboard motor, it is not possible to provide such a chamber of comparatively large volume directl at the cylinder exhaust outlet. Nevert eless, there is considerable space between the power head A of the motor and the propeller shaft housing 5. This space is utilized to accommodate an expansion chamber of proper size, as will presently appear.

part of the housing and of The tube proper is a tapered member 10 ex- V head 9 to the casing 5,or in the direction of flow, and the ratio of the upper end area to i2 naeomo the lower .end area may vary from 4:1 to 36: 1. In a van construction for example the upper en of the tube has a diameter of 4 inches at the int 12 where it merges into the center of t e head 9, and a diameter of 1}} inches at the lower end.

The unit is in its best running condition when the anticavitation plate 6 is submer ed about one inch, in which case the water me 10 is between the plate and the lower extremity of the tube 10 as illustrated in Figure 1. This condition is realized by properly building the boat and properly mounting the motor thereon. The device will of course operate 16 if more deeply immersed, but in such case the heavier parts of the propeller shaft hous ing and the exhaust tube w1ll be submerged. Inasmuch as these parts are not stream line, as illustrated in Figure 6, the resistance will so be increased.

As already indicated, it has been found that this type of tube eliminates the pulsations which occur in a straight exhaust pipe and further increases the volume of the ex- 25 haust expansion chamber.

Although a specific embodiment of the in- ;vention has been illustrated and described, it will be understood that various alterations in the details of construction may be made without departing from the scope of the invention, as indicated by the appended claims.

What -I claim is 1. The combination with a marine engine having an exhaust port, of a tapered exhaust '5 pipe connected with said port and leading to a point beneath the surface of the water, said pipe having a submersible outlet movable in accordance with the operation of said engine a and directed rearwardly with reference to its path of movement, whereby to eliminate back pressure from said pipe, the tapering form of said pipe being adapted to destroy ts resonance to pulsation -frequencies.

2. The combination with a two-cycle, twocylinder engine having exhaust ports, of a manifold member connected with the respec tive ports, and an exhaust pipe leading from said manifold member and of such dimensions as to be resonant to the frequencies oi pulsations occasioned therein by engine exaust through said ports, said pipe having a tapered form destructive to said pulsations.

3. In an outboard motor having a submersible lower unit provided with a rear- 55 wardly directed exhaust discharge port, the combination of a two-cylinder, two-c cle engine and a tapered exhaust pi lea ing from the cylinders of said engine t rou h the rearwardly directed discharge port 0 said lower unit, whereby to relieve back pressure and destroy frequency ulsations.

In testimony whereo I aflix mfisi ature.

FINN T. NS. 

